Global climate patterns stretching back 740,000 years have been confirmed by a three-kilometre-long ice core drilled from the Antarctic, Nature reports.

Analysis of the ice proves our planet has had eight ice ages during that period, punctuated by rather brief warm spells - one of which we enjoy today.

If past patterns are followed in the future, we can expect our "mild snap"
to last another 15,000 years.

The data may also help predict how greenhouse gases will affect climate.

Initial tests on gas trapped in the ice core show that current carbon dioxide (CO2) levels are higher than they have been in 440,000 years.

Nobody quite knows how this will alter our climate, but researchers hope a detailed picture of past fluctuations will give them a better idea.

Distant worlds

A large team of scientists, from 10 different countries, has spent most of the last decade extracting the mammoth column of ice from a location called Dome C, on east Antarctica's plateau.

The European Project for Ice Coring in Antarctica (Epica) aims to unlock the climatic secrets of our past - and in doing so gain a better understanding of what we can expect in the future.

The Antarctic camp was home to over 50 scientists

This is not the first ice core project - but it ventures much further back in time.

Dome C contains 800,000 years worth of snowfall, allowing Epica to obtain a climate record two times longer than its nearest ice core rival.

"We think this project will really change the way we look at climate," said co-author Eric W. Wolff, of the British Antarctic Survey, Cambridge, UK.

Each slice of the ice core tells tales about the distant world it came from.

For instance, scientists can work out climate by looking at the ratio of different types, or isotopes, of hydrogen atoms.

Different colds

Deuterium is a heavy isotope of hydrogen. If a sample of ice has a lot of it, that means the temperature was warmer - and vice versa.

"At very cold temperatures a great deal of the heavy isotopes have rained out," explained Jerry F. McManus, of Woods Hole Oceanographic Institution, US. "So all that is left is what we would call isotopically depleted or lighter. That is how we know how cold it was."

We think this project will really change the way we look at climate

Eric W. Wolff, the British Antarctic Survey, UK

He added: "You might say Antarctica is always cold - and you'd be right. But there is great variation in the degree of cold."

Another important thing that scientists can 'read' in the ice is the relative concentration of atmospheric gases.

That is because minute bubbles pock mark the core, within which tiny pockets of preserved air lie.

"That is the wonderful thing about ice cores," said Professor McManus. "There is air from three-quarters of a million years ago and it is still locked in these bubbles - it's incredible."

"The next ice age is not imminent," said Dr Wolff, "and greenhouse warming makes it even less likely - despite what The Day After Tomorrow says."

Every chunk of ice-core tells tales about the distant world it came from

Epica scientists hope that after they have fully analysed the ice core's atmospheric gases, they will gain a deeper knowledge of how climate relates to them.

"We will double the timescale over which we can study greenhouse gases," said co-author Thomas F Stocker, of the University of Bern, Switzerland. "We will be able to show what the natural variability is in relation to gases like CO2."

By understanding what greenhouse gases did to global temperature in the past, scientists might be able to predict the effect of humankind's enthusiastic CO2 belching.

"There is great controversy as to whether human beings have changed the climate," said Professor McManus. "But there is no doubt about the fact that human beings have changed the Earth's atmosphere. The increased levels of greenhouse gases are geologically incredible."

He added: "It is something of grave concern to someone like me, who sees the strong connection between greenhouse gases and climate in the past."